The AGC-kinases include the protein kinase C (PKC) and Rho-associated, coiled-coil containing protein kinase (ROCK) families. The PKC family of serine-threonine kinases transduce signals involving lipid second messengers. There are 9 genes that encode isozymes of PKC, several of which have splice variants. These isoforms are known as alpha, beta, gamma, delta, epsilon, zeta, eta, iota/lambda and theta (Nishizuka, Science 258, 607-614 (1992), Selbie et al., J Biol Chem 268, 24296-24302 (1993)). Based on sequence homology and biochemical properties, these PKC isozymes can be subdivided into three subgroups:
(a) the group of “conventional” PKCs comprising the alpha, beta, and gamma isozymes, which are all activated by calcium and diacylglycerol and can be stimulated by phorbol esters,
(b) the group of “novel” PKCs comprising the delta, epsilon, theta and eta isozymes, which are all calcium-independent, but diacylglycerol- and phorbol ester-sensitive, and
(c) the group of “atypical” PKCs, the zeta and iota (lambda in rodents) isozymes, which are insensitive to calcium, diacylglycerol and phorbol esters, but are activated by other lipids.
Members of the PKC family have been implicated in several disease states that could be treated by a PKC inhibitor. This application focuses on inhibitors directed against one isozyme, novel PKC epsilon, which has roles in pain, anxiety, addiction, inflammation, cardiac and cerebral ischemia, cancer, and diabetes. Embodiments of this invention for these and related indications are described below.
One embodiment of this invention is the development of a PKCε inhibitor for the treatment of pain. Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. It is an extremely common complaint and accounts for over 40% of outpatient medical visits in the US each year, resulting in more than $100 billion in health care costs and lost productivity. Pain can be classified according to its pathophysiology, as inflammatory, widespread (generalized), or neuropathic. Inflammatory and partially widespread pain is caused by activation or sensitization of peripheral nociceptors, which are the peripheral sensory neurons that detect noxious stimuli. Neuropathic pain results from injury mainly to the peripheral nervous system. Acute pain is often inflammatory and accompanies trauma, dysfunction of viscera, inflammation, or infection. Chronic pain persists beyond the usual course of an acute episode, generally longer than 1 to 6 months, and may be inflammatory, widespread, or neuropathic, or a combination of these.
Pain medications are widely prescribed, accounting for about 12% of all outpatient prescriptions written in the US, and also constitute a huge over-the-counter market. The most widely used are non-steroidal anti-inflammatory drugs (NSAIDS), opioid analgesics, monoamine reuptake inhibitors, and anticonvulsants. Many have serious side effects that limit their use. NSAIDs can cause GI bleeding and renal insufficiency, and the COX-2 inhibitors in particular carry increased risk of cardiovascular events. Tricyclic antidepressants can cause autonomic dysfunction, and in high doses, arrhythmias and hypotension. Opioids are sedating, frequently cause nausea and constipation, and in high doses produce respiratory depression. They also induce tolerance and in a minority of patients can lead to addiction. Side effects associated with the anticonvulsants gabapentin and pregabalin include somnolence, fatigue, dizziness, ataxia and weight gain. Because of these limitations, and a lack of efficacy especially for chronic pain syndromes, there is still a major need for developing more effective pain mediations with an improved side effect profile. There are many ongoing clinical pain trials in the US. For example, a recent search of the ClinicalTrials.gov website even when restricted to the term “pain in rheumatoid arthritis” revealed nearly 200 proposed, ongoing, or recently completed trials. Therefore, as an example, performing a later-phase clinical trial on pain in rheumatoid arthritis patients is very feasible.
WO 00/01415 and U.S. Pat. No. 6,376,467 describe the use of inhibitors of PKC epsilon in the treatment of pain, in particular chronic hyperalgesia and/or inflammatory pain (reference is also made to WO 02/102232 and WO 03/089457). As examples of suitable inhibitors, both peptides as well as small molecules are mentioned. WO 97/15575 and WO 01/83449 describe modulators of PKC with specific binding activity with respect to PKC epsilon. Peptide inhibitors that provide isozyme-specific modulation of PKC (in particular of PKC gamma and PKC epsilon) are described in WO 03/089456 and WO 03/089457.
For the sequence of human PKC epsilon, reference is made inter alia made to Basta et al., Biochim Biophys Acta, 1132 (1992), 154-160, as well as to SWISS-PROT entry Q02156 and EMBL entry X65293.
WO 03/04612 describes the use of inhibitors of PKC theta as an immunosuppressive agent (e.g. during organ transplant) and for treatment of systemic lupus erythematosus. Reference is also made to Castrillo et al., J Exp Med, 194, 9 (2001), p 1231-1242, who describe that PKC epsilon plays a role as a mediator in signaling cascades in activated macrophages.
The art also describes that PKC isozymes are associated with the metabolic diseases of diabetes and obesity. The link between PKC epsilon and these disorders has been established in two model systems for diabetes and obesity, viz the sand rat Psammomys and the High Fat Fed Rat. Reference is inter alia made to Shafrir et al., Annals New York Academy of Sciences 892 223-241 (1999), Donelly and Qu, Clin. Exper. Pharmacol. Phsyiol. 25: 79-87 (1998) and Qu et al., Journal of Endocrinology 162: 207-214 (1999). The latter two references also suggest that another novel PKC isozyme, PKC theta, may be involved in diabetes and obesity.
Other PKC isozymes have also been linked to diabetes and obesity; reference is inter alia made to U.S. Pat. No. 6,376,467, U.S. Pat. No. 6,284,784, U.S. Pat. No. 6,080,784, U.S. Pat. No. 6,057,440, U.S. Pat. No. 5,962,504, WO 02/22709, WO 01/30331, WO 96/40894 and the further references cited therein. U.S. Pat. No. 6,057,440, U.S. Pat. No. 5,698,578 and U.S. Pat. No. 5,739,322 describe the use of bisindolylmaleimide compounds as inhibitors of PKC beta in the prevention and treatment of diabetes and diabetes-related complications. These aforementioned patent applications and patents also describe an assay that can be used to determine the specificity of a given inhibitor for one isoform of PKC compared with another (referred to in these patents as the “PKC Enzyme Assay”). German patent application DE 197 40 384 A1 describes that antisense oligonucleotide sequences specific for certain PKC isozymes, and in particular against the alpha, delta, epsilon and zeta isoforms, may be used in the prevention or treatment of complications associated with diabetes. WO 01/81633 describes the association on PKC zeta with diabetes. Similarly, WO 94/18328 describes that the “atypical” PKC isozyme iota is involved in diabetes.
The art also describes that PKC epsilon is important for several neuropsychiatric disorders besides pain. WO 00/01805 describes PKC-epsilon knockout mice. This animal model is used to demonstrate that PKC epsilon can be used as a target for drugs to reduce anxiety, modulate alcohol consumption and drug abuse, addiction, withdrawal syndrome, muscle spasms, convulsive seizures, epilepsy and to modulate the action of drugs that target the GABA-A receptor.
US 2003/0134774 describes the use of inhibitors of PKC epsilon and PKC theta in inhibiting the onset of a cardiac disorder (e.g., hypertensive heart disease, valvular heart disease, diabetic heart disease, ischemic heart disease, etc.) and the progression of heart failure.
For other potential uses of inhibitors of PKC and/or of specific isoforms of PKC, reference is for example made to US 2002/0164389, US 2003/0118529, US 2003/0176424, US 2003/0176423, US 2003/0166678, US 2003/0134774, US 2003/0166678, US 2003/0176424, US 2003/0199423, WO 03/82859, WO 02/103000 and WO 02/87417.